6. Project Summary/Abstract A combined positron emission tomography myocardial perfusion imaging (MPI) and computed tomographic angiography (PET/CTA) study permits co-registration of anatomic images and functional data, thereby, identifying which coronary lesions cause significant functional deficits. The addition of PET MPI should increase the specificity of "significant" lesions detected by CTA and, thus, increase its positive predictive value. The addition of CTA should increase the specificity of PET MPI for the detection of ischemia produced by significant epicardial disease. The combination of the two also enhances rational planning for revascularization, by performing PCI only on lesions that have demonstrated consequences, resulting in better candidate selection, cost savings, and improved outcome. Our hypothesis is that PET/CTA improves diagnostic accuracy and expands diagnostic information that changes clinical decision-making and reduces costs associated with the management of patients with suspected significant CAD. The following are the aims of this pilot proposal: Aim 1: To perform a retrospective, randomized blinded analysis to determine whether PET/CTA changes clinical decision-making. Aim 2: To perform a cost analysis to determine whether PET/CTA reduces the costs associated with the management of patients with suspected ischemia. Aim 3: To determine the diagnostic accuracy of PET/CTA using invasive coronary angiography as the standard of reference This is a single center study enrolling 64 consecutive patients who have been referred for invasive coronary angiography (CA) and have had a prior single positron emission computed tomography emission (SPECT) MPI within 2 months of recruitment. All patients will undergo PET/CTA imaging prior to any coronary intervention. For the analysis of diagnostic accuracy, the SPECT and PET/CTA results are compared to the CA results. For the clinical decision-making analysis, the SPECT and PET/CTA studies are separated and randomized into two clinical scenarios: 1) patients with only the SPECT information available, and 2) patients with only the PET/CTA information available. Three cardiologists blinded to the original clinical decisions will determine the "theoretical" management of the patients after reviewing a randomized set of 64 SPECT studies and a randomized set of 64 PET/CTA studies. For the cost analysis, current market costs associated with noninvasive and invasive testing will be calculated. The overall goal of the pilot study is to confirm our hypothesis using limited and retrospective data. Using the pilot data, we plan to perform a larger, prospective randomized trial with a "real" world analysis and outcome data.